Background
I am working with the Campus Center for Appropriate Technology on refurbishing their Mobile Energy Operation Wagon. It was stolen and vandalized so the goal is to restore and improve it's aesthetics and begin restoring it's operability. The outside has to get painted in a way that will represent CCAT. Solar panels need to get remounted and batteries need to be bought and installed if time allows. I will be working on this project during the 2012 spring semester and at the minumum, will have the MEOW's aesthetics restored and the solar panels mounted. I hope to work even further onto installing the batteries. I will be working at the Campus Center for Appropriate Technology, located on the HSU campus.
Problem statement
The objective of this project is to restore the Mobile Energy Operation Wagon. I will be making it look more attractive by painting it to better represent CCAT. At the minumum, the solar panels will also be reinstalled.
Evaluation Criteria
This section was created to weigh the amount of work and budget that goes into each aspect. The goal of this project is to restore CCAT’s MEOW, paying special attention to aesthetics, so it can be modified for efficiency in a future project. I want to focus on durability, aesthetics and educational value as well as the obvious safety factor, so my project lays a good foundation for future projects.
| Criteria | Constraints | Weight (0-10) |
|---|---|---|
| Cost | must meet the budget | 7 |
| Safety | must be safe for everyone, especially since we’re dealing with electricity | 10 |
| Maintainability | must be perform maintenance work on fairly easily, strive for simplicity | 7 |
| Durability | must be built structurally sound and built to last | 8 |
| Aesthetics | must be pleasant to look at | 9 |
| Efficiency | must be as least as efficient as the previous design | 7 |
| Operability | must be able to operate with one or two people | 8 |
| Educational Value | must be easily comprehensible upon first glance, and able to educate citizens in detail | 9 |
| Mobility | must be able to be transported, the lighter the better | 5 |
| Modular Expandability | must be able to adapt and expand for future design and improvement | 8 |
Literature Review
This is a review of literature that may be used to reference while working on CCAT’s MEOW. My main focus on this project is mounting the photovoltaic panels, so my literature review will focus on the relevant subjects.
Photovoltaic basics
Photovoltaic systems consist of a photovoltaic generator (solar panel), power conditioning electronics, and storage facilities. A single photovoltaic panel that may be coupled with other panels to form a bigger system is called a module, and the finished system, an array. The panels consist of a frame, usually stainless steel or aluminum, and solar cells, which are lined with glass and backed with a polymer film. This allows maximization of light capture and keeps the temperature of the solar cells as low as possible to increase efficiency.[1] Photovoltaic panels present a pollution-free unlimited energy source, but are presented with a high cost for the cells, energy storage, and operating lifetime. [2] The panels I have available for this project are 4 REC Solar REC230PE panels. From the company’s website, “REC modules have an industry leading energy payback time of one year. This is a result of innovations such as the new fluidized bed reactor (FBR) silicon production process which uses 80 to 90 percent less energy than traditional methods”. Each panel weighs 39.6 lbs, and the dimensions are 65.50 x 39.02 x 1.50 inches. [3]
Photovoltaic concerns
Some concerns for this project are rack sturdiness, ability to achieve optimum tilt angle, and Energy Return on Investment (EROI). The group building the previous rack had problems with rack stability initially. [4] I will take this concern into account and build off of the previous mistakes and solutions. The tilt angle was previously difficult to reach at 30 degrees, and after discussing the project with CCAT, a big interest is building the rack so that it is capable of an even bigger tilt angle. [4] The final concern is for the EROI. Creating a positive ROI is not the goal of my project, but I may include the EROI into consideration when acquiring materials so a future project of creating a positive ROI is not made more difficult by my materials used.
Types of Panel Orientations
Solar panels may either be fixed or have some sort of tracking ability to follow the sun. CCAT has expressed a lot of interest in optimizing the tilt angle throughout various seasons, so that is where I will focus my research.
Fixed
The most efficient angle of a solar panel is facing directly at the sun. This can be determined by subtracting the latitude the panel is used at from 90 degrees, because the most efficient angle is the angle of latitude from vertical. In the summer, the optimal angle adds 15 degrees from the horizontal, and in the winter subtracts 15 degrees. Exact adjustments are not incredibly important because these 15 degree adjustments account for only 5% of the systems efficiency. [5] I subtract the latitude from 90 degrees because I will want to know the angle from the horizontal. Arcata lies at 40.9 degrees north; this gives an optimum year-round fixed angle of 49.1 degrees from the horizontal, a summer angle of 64.1 degrees, and a winter angle of 34.1 degrees.
1 or 2 Axis Tracking
Tracking systems are adjustable to “track” the sun throughout the day. A 2-axis tracking system, compared to a fixed tilt system increases the efficiency of the module 30-50%. [6] “For a nonconcentrating array, [a tracking system] is probably not worth the mechanical complexity involved, but if the array is portable, someone could turn it occasionally to face the sun.” [5]
Horizontal
On cloudy days, energy capture comes from diffuse solar radiation, rather than direct sunlight. In this case, a panel with a fixed horizontal orientation captures up to 50% more energy than a 2-axis tracking system. [6] Eureka averages 188 days of cloudy cloud cover (coverage of 8/10 or more), based on daylight hours only.[7]
References
- ↑ Solar Power Systems: ECE Energy Series No. 11. New York: United Nations, 1993.
- ↑ Bube, Richard and Fahrenbruch, Alan. Fundamentals of Solar Cells. New York, Academic Press, 1983.
- ↑ Solar Electric Supply, Inc, 2011. http://www.solarelectricsupply.com/solar-panels/26/RECSolar_REC240PE-USBLK.html.
- ↑ 4.0 4.1 Scott and Yvonne, 2005. Appropedia. http://www.appropedia.org/CCAT_MEOW_rack.
- ↑ 5.0 5.1 Komp, Richard. Practical Photovoltaics. Michigan: aatec publications, 1995.
- ↑ 6.0 6.1 Kelly, Nelson, and Thomas Gibson. 2009. Improved Photovoltaic Energy Output for Cloudy Conditions with a Solar Tracking System. Solar Energy. 83, no. 11: 2092.
- ↑ http://www.wrcc.dri.edu/htmlfiles/westcomp.ovc.html
Costs
Because the goal of this project is to restore the trailer and get the panels mounted, I am only concerned with costs related to those components. The panels are already in possession, donated by David Katz of AEE Solar. The paint cost was based on an acquaintance of mine recently painting a short bus with spray paint. I tripled the cost the bus was painted for to allow flexibility and to ensure a lasting paint job. The reason I chose spray paint is that it is what the bus was painted with and I do not know much about brush on paint. The paint idea is open to suggestions. My main focus is on the rack. I am choosing to base my proposed budget on a Uni-Rac system plus some extra budget for something like a car jack I may end up using. The goal would be to mount the panels much cheaper. A past proposal for the MEOW project shows a possible 40% discount on a Uni-Rac system, this may be something that is looked into.
| Quantity | Item | Source | MSRP (each) | Amount needed |
|---|---|---|---|---|
| 4 | PV Panels | David Katz (AEE Solar) | $565 | $0 |
| 1 | Rack | Miscellaneous | $500 | $500 |
| 6 | Spray Paint (pack of 6) | Harbor Freight Tools | $36 | $216 |
This creates a total proposed budget of $716.